This invention relates to a movable lever which cooperates with a tensioner to impart tension to a chain transmitting power from a driving sprocket to one or more driven sprockets in an automobile engine.
In general, in a power transmission as an automobile engine timing drive or the like, an endless transmission chain circulates around a driving sprocket and one or more driven sprockets, and a lever, pivotally mounted on an interior wall of the engine by a mounting bolt, mounting pin, or the like, is in sliding engagement with the chain, and cooperates with a tensioner to impart appropriate tension to the chain.
In a conventional movable lever for a transmission, as shown in FIG. 5, a lever body 10 includes a shoe 11 having a surface on which a traveling transmission chain (not shown) is in sliding contact, and a plate-receiving portion 12 extending longitudinally on the back side of the shoe 11. The shoe and plate-receiving portion are integrally molded of synthetic resin. A steel reinforcing plate 20, which reinforces the lever body 10, fits into an open slot 12a in the plate-receiving portion 12, the slot extending along the longitudinal direction of the lever. The lever body and reinforcing plate are mounted on an inner wall (not shown) of an engine by a mounting bolt P (FIG. 6), which is inserted through cofastening mounting holes 12b and 21 provided in the lever body 10 and the steel reinforcing sheet 20, respectively.
A plurality of reinforcing ribs 12e, such as shown in FIGS. 5 and 6, are formed on a side of the plate-receiving portion 12. These reinforcing ribs are disposed in an array which extends from the vicinity of the mounting hole 12b along the lever in the longitudinal direction. The reinforcing ribs 12e prevent deformation of the lever body 10, which is likely to occur as a result of sliding contact with the transmission chain, and also enhance the strength of the lever body 10.
Where a conventional movable lever is used, engine oil O, in the form of a mist produced during operation of the engine, agglomerates and adheres to the lever body 10. However, the flow of the engine oil toward the mounting hole 12 is impeded by the plurality of reinforcing ribs 12e. Accordingly, it is not possible for adequate quantities of engine oil to reach, and flow into, the mounting hole 21 in the steel reinforcing sheet 20. As a result seizing of the steel reinforcing sheet 20 to the mounting bolt P can occur, preventing pivoting of the lever.
The problem of seizing between the steel reinforcing sheet 20 and the mounting bolt P, can be avoided if the movable lever formed entirely of resin, and the steel reinforcing sheet 20 is eliminated. However, if the reinforcing sheet is eliminated, the strength of the lever is reduced, and the durability of the lever is significantly impaired, especially when the lever is used in a high temperature environment.
Accordingly, the principal objects of the invention are to solve the above-described problems, and to provide a movable lever, which is able to avoid seizing on a mounting bolt or other supporting shaft by effectively utilizing engine oil as a lubricant, and which is able to pivot smoothly in cooperation with a tensioner and thereby impart appropriate tension to a transmission chain.
To address the above objects, the movable tensioning lever in accordance with the invention comprises an elongated lever body and a steel reinforcing plate. The lever body includes a shoe having front and back sides. The front side is a surface for sliding contact with a chain. The lever body also includes a plate-receiving portion on the back side of the shoe, extending along the longitudinal direction of the lever body, and having an elongated slot also extending along the longitudinal direction of the lever body and opening in a direction facing away from the shoe in a direction perpendicular to the front side. The shoe and plate-receiving portion are integrally molded as a unit from synthetic resin. The steel reinforcing plate fits into the slot, and the lever body and reinforcing plate have coaxial mounting holes in register with each other adjacent one end of the lever body for cofastening engagement with a supporting shaft mounted on an inner wall of an engine. Reinforcing ribs are formed on a laterally outward facing surface of said plate-receiving portion. The reinforcing ribs are disposed in an array extending from the vicinity of the mounting holes along the plate-receiving portion in the longitudinal direction of the lever body. In accordance with the invention, oil guide grooves, for guiding oil to the mounting holes, are composed of notches formed in end portions of the reinforcing ribs.
The synthetic resin of which the lever body is composed is not particularly limited. Synthetic resins such as nylon 6, nylon 66, all aromatic nylons and the like, known as xe2x80x9cengineering plastics,xe2x80x9d have superior durability and lubricating properties, and are preferably used, since the chain-contacting sliding surface functions as a shoe. Where exceptional strength is required, a fiber-reinforced resin may also be used.
The array of reinforcing ribs, which extends from the vicinity of the co-fastening mounting holes along the longitudinal direction of the lever, may have any of a wide variety of configurations, such as a truss form, a wave form, a vein-shaped form, and the like.
The depth of the oil guiding groove can vary. For example, the notches which constitute the groove can extend to the full depth of the ribs, or can extend partially through the depths of the ribs. For example, notches which extend through half the depth of ribs can provide improved results in guiding oil toward the co-fastening mounting holes.
The lever can be mounted on any of various mounting devices provided on an inner wall of an engine, including a mounting bolt, a pin, or other shaft-type support.
With a movable lever for a transmission chain according to the invention the following benefits can be obtained.
When a floating mist of oil generated in an engine during operation agglomerates and adheres to a lever mounted upright on a shaft on an inner wall of an engine, the oil flows downward along the longitudinal direction of the lever.
The oil passes smoothly downward through the oil guide groove constituted by notches formed in end portions of the reinforcing ribs. The flow of oil takes place without being impeded by the multiple reinforcing ribs, and the oil flows into the mounting hole of the lever body and into a cofastening mounting hole of the steel reinforcing plate, so that the oil penetrates between the steel reinforcing plate and the supporting shaft.
Lubricant is always present in adequate quantity between the reinforcing steel sheet and the mounting shaft. Consequently, appropriate tension is imparted, by a tensioner, through the lever, to a transmission chain which slides along the shoe of the lever. The lever pivots smoothly on its mounting shaft about one end of the lever without seizing between the steel reinforcing plate and the shaft.